1. Technical Field
The present disclosure relates to a photographing lens system, and more particularly to a combined photographing lens system.
2. Related Art
In recent years, with the rise of portable electronic device with photographing capability, the demand for compact photographing module is increased. The photo-sensing device of an ordinary photographing camera is commonly selected from a charge coupled device (CCD) and a complementary metal-oxide semiconductor (CMOS) device. In addition, with the advance of semiconductor manufacturing technology enabling the miniaturization of pixel size of sensors, the resolution of a compact optical lens assembly is gradually increased so there are increasing demands for the compact optical lens assemblies in the limited spacing capable of generating superior imaging quality.
In order to reduce manufacturing costs, a two-lens structure is adopted in a conventional photographic lens assembly. For example, U.S. Pat. No. 7,525,741 discloses a two-piece optical lens system for taking image consisting of two lens elements. However, this lens assembly with only two lens elements having limited aberration correction ability is unfavorable for meeting the demand for high-level photographing module.
In order to improve the imaging quality and miniaturize the overall size, a photographic lens assembly consisting of three lens elements is disclosed. For example, U.S. Pat. No. 7,564,635 discloses an optical lens system for taking image consisting of three lens elements. However, the refractive powers of the three lens elements of the lens assembly are all positive such that it is difficult to correct the aberration (i.e. chromatism) of the lens assembly, therefore, affecting the imaging quality. In view of this, there is a need that a photographing optical lens assembly applicable for compact and portable electronic products has superior imaging quality and an appropriate total length of the lens elements.